1. Field of the Invention
This invention relates to an apparatus and a process for the reproducible withdrawal of an adjustable, amount of a liquid or an active substance from a container such as a glass vial.
A dosage metering apparatus includes a pre-chamber in free flow communication with the interior of a container, the pre-chamber being initially filled with an amount of liquid from the container and in communication with a measuring chamber. The measuring chamber has a pre-defined but adjustable volume and is in communication with a closeable outlet, so that after the amount to be withdrawn from the measuring chamber has been adjusted, it is not necessary for the user to perform any additional manipulations, such as shaking the container or separating the dosage metering apparatus from the container, to affect the discharge of a precise amount of liquid from the container.
2. Prior Art
In many fields of application it is necessary to repeatedly withdraw a precise dosage of a liquid pharmaceutical preparation or active medication substance from within a container. This is commonly achieved by pouring the contents of the container into a receptacle having a measuring scale marked on it. However, this method of metering a dosage amount is imprecise because it relies upon the careful manipulation of the container by the user.
One solution is to provide the container or vial containing the liquid with a head or cap mechanism inserted in the neck of the vial which provides for the displaceable accession of air into the interior of the vial causing the liquid to flow from within the vial as countable drops. While devices of this type precisely meter a dosage amount, they fail to provide for rapid discharge of the liquid from the container. As a result of the slow manner in which liquid flows from the interior of the vial, i.e. by countable drops, the user often shakes the vial in an attempt to accelerate the discharge of liquid. Shaking the vial results in an incorrect dosage being discharged from the vial due to the liquid being supplied in such a fast drop sequence that it is difficult to accurately count the drops.
U.S. Pat. No. 4,951,839-Kong shows seven different embodiments of a dosing apparatus which provides for the precise, repeated withdrawal of an adjustable dosage of liquid from a container such as a glass vial. FIG. 6 of Kong shows a cup-shaped container (cup-shaped housing) having cylindrical walls, which via a cylindrical attachment means having adjustable attachment arms which can be pushed onto a plurality of differently sized container necks. Two volumes A and B are formed in the cup by an overflow edge of a substantially cylindrical accordion-like sleeve mounted on the bottom of the cup-shaped container. The accordion-like sleeve allows the upper edge in the cup-shaped attachable container to be shifted such that the volumes of A and B change in opposite directions. A flat snap cover closes the top end of the cup-shaped container and can be opened, so that after removing the container and the attachment means from the bottle neck the liquid amount dosed in the dosage space B by the adjusted level of the overflow edge of the accordion-like sleeve can be poured out or emptied. This requires the user to carefully remove the container and attachment means in order to avoid spillage.